线程1：EXC_BAD_ACCESS（code = EXC_I386_GPFLT）在UICollectionView中吗？

Question

我有一个UICollectionView

<div class="parent">
  
  <div class="line" style="">
    <span class="text">AND</span>
  </div>
</div>

然后在另一个我拥有的文件中

let cellIdentifier = "DayCollectionViewCell"
class ViewController: UIViewController, UICollectionViewDataSource,UICollectionViewDelegate {

    @IBOutlet weak var button: UIButton!
    var dates = [Date?]()
    var startDate: Date?
    @IBOutlet weak var daysCollectionView: UICollectionView!
    override func viewDidLoad() {
        super.viewDidLoad()
        daysCollectionView.register(UINib.init(nibName: "DayCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: cellIdentifier)

        let allDates = Helper.generateRandomDate(daysBack: 900, numberOf: 3)
        self.dates = allDates.sorted(by: {
            $0!.compare($1!) == .orderedAscending
        })
        print(self.dates)
        startDate = self.dates.first! ?? Date()

        daysCollectionView.delegate = self
        daysCollectionView.dataSource = self
        // Do any additional setup after loading the view, typically from a nib.
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 900
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = daysCollectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! DayCollectionViewCell     //ON THIS LINE!!!!! Thread 1: EXC_BAD_ACCESS (code=1, address=0x5b9c38eb4f78)

        let cellDate = Calendar.current.date(byAdding: .day, value: indexPath.item, to: self.startDate!)
        if self.dates.contains(where: { Calendar.current.isDate(cellDate!, inSameDayAs: $0!) }) {
            print("same")
            cell.backgroundColor = UIColor.red
        } else {
            print("not me")
            cell.backgroundColor = UIColor.lightGray
        }
        return cell
    }

}

然后添加DayCollectionViewCell.xib文件：

我在这里做错了什么？